Pivots for movably mounting a door to a door frame are well known. Door pivots typically comprise a bracket anchored to the doorjamb which pivotably cooperates with a second portion mounted to the face of the door. A door pivot differs from a hinge primarily in that the axis of rotation of a hinge is coincident to or outside the lateral edge of the door, whereas the axis of rotation of a pivot falls inside the lateral edge of the door. For oversized doors or doors in commercial installations which are subjected to a high volume of traffic, pivots provide certain mechanical advantages over hinges which make them desirable.
At least two door pivots, mounted one each at the top and bottom of the door, are required to mount the door to the frame. In high-traffic application or on large doors, one or more intermediate pivots may also be used, mounted at locations vertically intermediate the top and bottom pivots.
Door pivots are broadly categorized according to their intended mounting position on the door. All doors require at least two pivots, a top pivot and a bottom pivot. The bottom pivot is the privary load bearing pivot and typically includes a ball bearing located in the door portion of the pivot for enhanced load carrying capability. In contrast, top pivots do not bear as great a portion of the weight of the door as bottom pivots. Instead, top pivots are designed primarly to provide an upper pivot point for the door and to withstand lateral forces exerted against the door resulting from the torque applied to open the door. The lateral loads exerted against a top pivot exert a shear force against the screws holding the frame portion of the pivot to the header, rather than a tension force against the screws holding the door portion to the stile. Since screws under shear have a greater load bearing capability than screws under tension, the top pivot effectively withstands lateral loads but is not effective in resisting heavy vertical loads.
On oversized doors or doors in commercial installations which are subjected to high traffic volumes, a third type of pivot is often used, the intermediate pivot. Intermediate pivots, so called because they are mounted at locations vertically intermediate the top and bottom pivots, differ from top pivots primarily in that they are intended to bear more of a vertical load than top pivots. Intermediate pivots differ from bottom pivots primarily in that they must resist greater lateral forces than bottom pivots. Intermediate pivots thus present unique design challenges, since they must bear vertical loads like a bottom pivot while resisting lateral loads like a top pivot.
Door pivots may be further categorized as either center pivots or offset pivots, depending upon where the axis of rotation of the pivot lies in a vertical plane with respect to the door. With a center pivot, the axis of rotation falls in a vertical plane intermediate the inner and outer stiles of the door. Center pivots are primarily used when it is desired to mount a door which can pivot in both directions. However, in order to position the axis of rotation intermediate the stiles of the door, channels or recesses must be cut into the stiles to mount the pivot. While center pivots are acceptable for mounting interior or vestibule doors, the interruptions in the door required to mount a center pivot make the center pivot undesirable for exterior applications which require weather sealing, since the channels which are cut into the lateral edge of the door to mount the door pivot will permit air and water to pass through.
For such exterior applications which require weather sealing, the offset door pivot is the more desirable alternative. The bracket of the pivot assembly typically comprises a first leg portion which is mortised into and anchored to the jamb of the door frame. A second leg portion extends past the face of the door and includes a pivot interface for cooperating with a door portion of the pivot assembly. The door portion is typically mortised into the face of the door such that the edge of the door portion bears against the edge of the mortise to support the vertical load of the door. The pivot interface between the door portion and the bracket will typically include a spindle formed on one of the bracket or door portions, with a cooperating bore on the other member which receives the spindle for rotational movement therein.
One of the difficulties presented by a conventional offset door pivot is the requirement that the face of the door be mortised or otherwise machined to provide a horizontal surface against which the door portion can bear to support the vertical load exerted by the weight of the door. Mortising the door requires time, special machinery, and skilled labor, which increases the cost of installing the door pivot. Thus, there is a need to provide a door pivot wherein the door portion is capable of supporting a vertical load without the requirement that the face of the door be mortised.
Another problem associated with conventional intermediate offset pivots is that a given pivot assembly will be either left-handed or right-handed, depending upon the direction of the angle formed by the first and second legs of the bracket member. Such handed pivots double the inventory of pivots which a building supplier must keep on hand. Further, the possibility of error is introduced, in that a worker may arrive at the work site with, for example, a left-handed pivot to hang a right-handed door, thereby causing aggravation, delay, and increased cost of installation. Finally, there is the possibility that a worker may attempt, either accidentally or unknowingly, to install a wrong-handed pivot for a particular application. Thus, there is a need to provide a non-handed intermediate offset door pivot.